1. Field of the Invention
The invention in general relates to the field of medical, dental and therapeutic lavage, and more particularly to a mechanized lavage system in which the rate of fluid flow and the average fluid pressure, are variable.
2. Description of the Prior Art
Lavage, or the washing of tissue, is perhaps as old as medicine itself. In the early years it consisted of the application of fluid, generally a liquid such as water, to tissue to wash away dirt or debris. In more modern times, it has become more important, and more thorough, due to an awareness of bacteria and other organisms that may cause infection. In the last several decades, mechanized lavage systems have become common.
Before proceeding to the discussion of prior art mechanized devices it will be useful to clarify terminology. The word "lavage" is used ambiguously in the literature, sometimes referring to a pulsating stream type washing or therapy, sometimes referring to a stream type of washing, and sometimes also including an aspiration function. In this document, unless the context clearly indicates otherwise, "irrigation" shall mean the stream type of washing "pulsatile lavage" shall mean the pulsating type of washing, and the word "lavage" shall mean the broadest sense of the term, referring to any one of, or combinations of, irrigation, pulsatile lavage, and aspiration.
It will also be useful to note that in a system in which fluid is caused to flow through a tube, that the pressure of the fluid and the rate of fluid flow change in the same way. For example, if the pressure increases then so does the rate of flow, and if the rate of flow increases then so does the pressure. Thus some of the basic aspects of the invention, for example the controllability and variability aspects, may be discussed in terms of either rate of flow or in terms of pressure.
In addition, it is helpful to note that when the word pressure is used herein it will normally refer to the average pressure along a fluid stream in contrast to the instantaneous pressure which will vary in a stream having pulsations.
Mechanical lavage systems are disclosed in U.S. Pat. No. 3,540,437 issued to Troy, U.S. Pat. No. 3,912,168 issued to Mullins et al., U.S. Pat. No. 3,993,054 issued to Newman, U.S. Pat. No. 4,278,078 issued to Smith, and U.S. Pat. No. 4,294,251 issued to Greenwald et al. All the foregoing patents disclose apparatus for producing a pulsating fluid lavage stream in which the pulsation is fixed at a single frequency. Conceivably, other frequencies might be obtained with these systems by changing the frequency of rotation or reciprocation of the motors, although clearly under such circumstances the rate of fluid flow and pressure would change considerably as the frequency changed. U.S. Pat. No. 3,902,664 issued to Deines discloses a fluid pulsator in which the frequency of pulsation may be changed. Analysis of the system indicates that the change of frequency is accomplished by changing the back pressure created in the device and thereby altering the rate of flow of fluid through the device. In the latter patent it appears that although the instantaneous pressure within each individual pulse as it energes from the exit valve of the pulsating mechanism may remain approximately constant throughout a wide range of frequencies, it is also evident that the average pressure of the fluid flow will change considerably over the frequency range since the rate of fluid flow changes considerably. Furthermore, as the individual pulses move away from the exit valve of the pulsation creating device, the change in average pressure will cause the instantaneous pressure within each pulse to change well before it leaves the lavage tube.
Generally, the most modern medical lavage and irrigation systems have included suction (aspiration) functions for removing the lavage fluid. See for example U.S. Pat. No. 4,299,221 issued to Phillips et al. and U.S. Pat. No. 4,294,251 issued to Greenwald et al. This suction function has been found to be useful and necessary to remove the lavage fluid to create a clear field, for example, when the lavage is used to cleanse a wound during surgery, and also to remove the debris when pulsatile lavage is used for debridement purposes.
It appears that, in general, prior art medical lavage systems have been limited to single frequencies since the sudden and unpredictable change in fluid flow caused by the changing frequency in all prior art systems can cause considerable problems. For example, both the too much fluid and too little fluid situations can interfere with surgery, which could be serious if it occurred at critical times. As we will be seeing, the removal of this limitation by the present invention has resulted in many surprising advantages of having a variable frequency being discovered.
In the prior art, as well as in the present invention, if the rate of flow through the lavage system is changed, the average pressure of the fluid stream will also change, as long as the tubing and other parts constricting the flow remain unchanged in diameter. This normally causes little problem since the relationship between pressure and flow is a familiar one due to the almost constant contact with such pressurized flow systems, such as the faucet, etc., in the modern environment. Accordingly, most prior art lavage and irrigation systems include a means for altering the rate of flow (fluid pressure) of the system. Such controls appear to be universally of the throttle type control. See any of the above-cited patents. The throttle type control necessarily is inefficient since it causes the motor providing the irrigation or lavage function to waste energy as the motor struggles to force the fluid through a constricted opening. In most systems, the result is that the motor is ironically forced to produce the highest pressures precisely at the time when reduced pressure at the lavage head is used. In addition to wasted energy, such throttle systems result in shortened life for mechanical parts, and considerably increased operating noise of the system. These factors were perhaps not seen as disadvantages in the prior art system; however it has been found that the present invention has removed these characteristics in a unexpected and thorough fashion that now reveals them to be quite undesirable, when the controllability, quietness and efficiency of the lavage and irrigation system of the present invention is compared to the prior art.